System and method for concurrent visualization and quantification of blood flow using ultrasound

ABSTRACT

A system for visualization and quantification of ultrasound imaging data may include a display unit, and a processor communicatively coupled to the display unit and to an ultrasound imaging apparatus for generating an image from ultrasound data representative of a bodily structure and fluid flowing within the bodily structure. The processor may be configured to generate vector field data corresponding to the fluid flow, wherein the vector field data comprises axial and lateral velocity components of the fluid, extract spatiotemporal information from the vector field data at one or more user-selected points within the image, and cause the display unit to concurrently display the spatiotemporal information at the one or more user-selected points with the image including a graphical representation of the vector field data overlaid on the image, wherein the spatiotemporal information includes at least one of a magnitude and an angle of the fluid flow.

RELATED APPLICATION

This application claims the benefit of and priority to U.S. ProvisionalNo. 62/478,828, filed Mar. 30, 2017, which is incorporated by referencein its entirety.

BACKGROUND

Vector flow imaging (VFI) can be used to visualize and quantify complexblood flow measurements in cardiovascular applications for betterdiagnosis of stenosis and other conditions of the vascular system. Sinceconventional Doppler ultrasound only allows velocity estimation alongthe axial direction, new vector flow imaging techniques have beenintroduced to allow multi-directional velocity estimations. These newtechniques include fixed-arrow-based (see FIG. 7A, free-arrow-based (seeFIG. 7B), and pathlet-based visualization (see FIG. 7C).

For fixed-arrow-based visualization, the magnitude of flow velocity isencoded as color intensity, and is proportional to the length of thearrow. The direction of flow velocity is shown both by the arrow andcolor. The tail of the arrow is fixed in space. For free-arrow-basedvisualization, free arrow is used to dynamically track the blood flow.The magnitude of flow velocity is color encoded, and is proportional tothe length of the arrow. The direction of flow velocity is indicated bythe arrow. In the context of VFI, streamline may be defined as a familyof curves that are instantaneously tangent to the velocity vector of theflow, and a pathline can be defined as a family of trajectories that theflow particles would faithfully follow during flow.

For pathlets-based visualization, dynamic curve tracing of the flowtrajectory is achieved by curved pathlets. Pathlets can be seen as theshort, frontal segments or parts of the pathlines, that start to fadeout when distance from the tip exceeds a given threshold, which isdefined as the pathlet length. The magnitude of flow velocity is colorencoded, and is proportional to the length of the pathlets. Thedirection of flow velocity is indicated by the moving direction ofpathlets. Overall, among the three visualization methods, pathlet-basedvisualization is generally the most intuitive method with potential toreplace the other visualization methods for VFI.

While an improvement over Doppler, existing implementations of these VFItechniques may still have limitations. For example, in existingfixed-arrow-based visualization specifically, the color-coding map forvelocity magnitude and direction is complex and not intuitive.Additionally, the length of the arrow is not a direct measurement ofvelocity magnitude. In existing free-arrow-based visualizationtechniques, the arrows are typically straight lines and may not be goodrepresentations of curved trajectories and having an arrowhead for eachstreamline may clutter the visualization and thus be less intuitive.Also, in existing free-arrow-based and pathlets-based visualizations,neither the coded color map nor the length of the arrow (pathlet) is adirect measurement of velocity magnitude. Consequently, directmeasurements and accurate quantification of blood flow are unavailable.Additional shortcomings of existing VFI techniques may include theinability to perform point measurements of blood flow at certainlocations of interest, which can further limits the capability of VFI toextract detailed spatiotemporal information of blood flow. Examples inaccordance with the present disclosure may address one or more of theshortcomings of existing VFI systems and methods.

SUMMARY

The present invention provides systems and methods for concurrentultrasound vector flow imaging (VFI) with automatic curve tracking. Theexamples described herein may overcome limitations of existing VFItechniques, for example by providing more user friendly and/orinteractive displays of VFI image data to enable the user to selectspecific points within the blood flow, obtain the velocity magnitude ata selected point, and/or by utilizing arrow displays to more intuitivelyvisualize the velocity vector data at the user selected points.

A system for visualization and quantification of ultrasound imaging datain accordance with the present disclosure may include a display unit,and a processor communicatively coupled to the display unit and to anultrasound imaging apparatus for generating an image from ultrasounddata representative of a bodily structure and fluid flowing within thebodily structure. The processor may be configured to generate vectorfield data corresponding to the fluid flow, wherein the vector fielddata comprises axial and lateral velocity components of the fluid,extract spatiotemporal information from the vector field data at one ormore user-selected points within the image, and cause the display unitto concurrently display the spatiotemporal information at the one ormore user-selected points with the image including a graphicalrepresentation of the vector field data overlaid on the image, whereinthe spatiotemporal information includes at least one of a magnitude andan angle of the fluid flow. In some embodiments, the ultrasound imagingapparatus may be provided by an ultrasound diagnostic system includingthe display and the processor, and the ultrasound diagnostic system maybe configured to generate and update the image in real-time whileultrasonically imaging the bodily structure.

In some embodiments, the processor may be configured to generate apathlet-based graphical representation of the vector field data. In someembodiments, the graphical representation of the vector field data mayinclude a vector map that includes a flow mask layer defining asub-region corresponding to the vector field data and a vectorvisualization layer illustrating at least partial trajectories ofvelocity vectors in the sub-region. In some embodiments, the processormay be configured to define the flow mask based on image segmentation,available vector field data (e.g., blood flow velocity data), userinput, or combinations thereof.

In some embodiments, the processor may be configured to dynamicallyupdate the flow mask in subsequent image frames based on temporalvariations of available velocity estimates in subsequent vector flowframes. In some embodiments, the processor may be configured to generatethe B-mode image and the graphical representation of a vector field inreal time while acquiring the echo signals. In some embodiments, theprocessor may be configured to dynamically update the flow mask insubsequent image frames based on temporal variations of the availablevector field data in corresponding vector flow frames. In someembodiments, the processor may be configured to cause the display unitto display, as the spatiotemporal information, a graph of the at leastone of the magnitude and the angle of the fluid flow at the one or moreuser-selected points as a function of time. In further embodiments, theprocessor may be configured to cause the display unit to display, as thespatiotemporal information, a visual representation of a direction ofthe fluid flow at the one or more user-selected points, and the visualrepresentation may be dynamically updated by the processor to reflecttemporal changes in the direction of the fluid flow. In someembodiments, the visual representation of the direction of the fluidflow may be in the form of a graph of the axial component of thevelocity vector versus the lateral component of the velocity vector atthe one or more user-selected points. In further embodiments, theuser-selected points may define a selected region including a pluralityof adjacent points (e.g., a cluster of pixels on the displayed image)and spatiotemporal data may be displayed for each of the points in theselected region individually or in combination (e.g., as an average overthe selected region).

In some embodiments, the vector flow data may also include elevationalvelocity components of the fluid, and the processor may be configured togenerate a three dimensional (3D) image of the ultrasound data overlaidwith a graphical representation of a 3D velocity vector field. In someembodiments, the processor may be configured to estimate the axial,lateral, and/or elevational velocity components of the fluid flow. Forexample, the system for visualization and quantification according tothe present disclosure may be integrated with an ultrasound imaginingsystem configured to acquire the ultrasound imaging data. In otherembodiments, one or more of the components of the system may be part ofa stand-alone visualization system communicatively coupled to a sourceof ultrasonic imaging data, which may be pre-stored or received inreal-time. For example, at least one of the display and the processormay be part of a workstation separate from the ultrasound imagineapparatus, and may be configured to generate the ultrasound image fromreal-time or pre-stored ultrasound imagining data. In further examples,the processor may receive the estimated components as input and generatethe image and extract spatiotemporal information for concurrent displaywith the image.

A method according to some embodiments of the present disclosure mayinclude generating an image from ultrasound data representative of abodily structure and fluid flowing within the bodily structure,generating vector field data corresponding to the fluid flow, whereinthe vector field data comprises axial and lateral velocity components ofthe fluid, displaying, on a user interface, a graphical representationof the vector field data overlaid on the image, extractingspatiotemporal information from the vector field data at one or moreuser-selected points within the image, and concurrently displaying thespatiotemporal information at the one or more user-selected points withthe image including the graphical representation of the vector fielddata, wherein the spatiotemporal information includes at least one of amagnitude and an angle of the fluid flow. In some embodiments, themethod may include receiving, in a processor, signals responsive toultrasonically scanning a region of interest (ROI) of a subject, andgenerating a B-mode image of the ROI responsive to the signals andestimating axial and lateral components of blood flow velocity within asub-region of the ROI to obtain a vector field of the blood flow in thesub-region. Graphical representations of the vector field may begenerated by the processor and concurrent displays of the vector fieldand spatiotemporal information about the vector field may be provided inaccordance with any of the examples herein. In some embodiments, thegraphical representation may be a pathlet-based graphical representationof the vector field.

In embodiments, the displaying of spatiotemporal information may includedisplaying a graph of the at least one of the magnitude and the angle ofthe fluid flow at the one or more user-selected points as a function oftime. In some embodiments, the displaying of spatiotemporal informationmay include displaying a visual representation of a direction of thefluid flow at the one or more user-selected points, and the visualrepresentation may be dynamically updated to reflect temporal changes inthe direction of the fluid flow. In further embodiments, the visualrepresentation of the direction of the fluid flow may be in the form ofa graph of the axial component of the velocity vector versus the lateralcomponent of the velocity vector at the one or more user-selectedpoints. In yet further embodiments, the displaying of spatiotemporalinformation may include displaying information for the magnitude and theangle of the fluid flow, and wherein the displayed information and forthe magnitude and the angle of the fluid flow are synchronously updatedin real-time responsive to the signals received from a region ofinterest (ROI) in a subject. As described herein, one or more points maybe selected by a user and spatiotemporal information may be provided forthe selected points. In some examples, the selected points may include aplurality of adjacent points in the image (e.g., a cluster of points ora selected region) and spatiotemporal information may be displayed foreach point in the selected region either individually or collectively(e.g., as an average) for all points in the elected region. Inembodiments of the present disclosure, the displayed spatiotemporalinformation and the graphical representation of the vector field may besynchronously updated in real-time responsive to real-time signalsreceived from the ROI. In some embodiments, the graphical representationof the vector field data may include a vector map comprising a flow masklayer delineating a region corresponding to the vector field data inthat frame and a vector visualization layer illustrating at leastpartial trajectories of at least some of the velocity vectors in thevector field data in that frame

In some embodiments, the method may further include estimatingelevational velocity components of the fluid to obtain three dimensional(3D) vector field data for a volumetric region of interest (ROI). Insuch embodiments, the concurrent displaying of spatiotemporalinformation at the one or more user-selected points with the image mayinclude displaying 3D image of the volumetric ROI overlaid with the 3Dvector field data.

Any of the methods in accordance with the present disclosure, or stepsthereof, may be embodied in non-transitory computer-readable mediumcomprising executable instructions, which when executed may cause aprocessor of medical imaging system to perform method or steps embodiedtherein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is block diagram of a visualization and quantification system inaccordance with the present disclosure.

FIG. 2 is a block diagram of a visualization and quantification systemin accordance with further examples of the present disclosure.

FIG. 3 is an ultrasound image generated in accordance with examples ofthe present disclosure, which includes a background B-mode imageoverlaid with a vector flow image visualizing the blood flow patternwithin the left ventricle of a human heart.

FIG. 4 shows an illustration of a portion of two consecutive frames ofultrasound image data and a technique for updating the pathlet-basedinformation in the frames.

FIG. 5 shows a screen capture of a display unit displaying an exampleset of images generated in accordance with the present disclosure, whichdisplay a relatively smooth blood flow in a vessel.

FIGS. 6A and 6B show other screen captures of a display unit displayingother example sets of images generated in accordance with the presentdisclosure, which show a more turbulent blood flow pattern within ahuman carotid artery.

FIGS. 7A, 7B, and 7C show additional examples of vector flow imagesgenerated using other VFI visualization techniques.

FIG. 8 shows a block diagram of an ultrasound imaging system inaccordance with further examples of the present disclosure.

DESCRIPTION

The following description of certain exemplary embodiments is merelyexemplary in nature and is in no way intended to limit the invention orits applications or uses. In the following detailed description ofembodiments of the present systems and methods, reference is made to theaccompanying drawings which form a part hereof, and in which are shownby way of illustration specific embodiments in which the describedsystems and methods may be practiced. These embodiments are described insufficient detail to enable those skilled in the art to practice thepresently disclosed systems and methods, and it is to be understood thatother embodiments may be utilized and that structural and logicalchanges may be made without departing from the spirit and scope of thepresent system. Moreover, for the purpose of clarity, detaileddescriptions of certain features will not be discussed when they wouldbe apparent to those with skill in the art so as not to obscure thedescription of the present system. The following detailed description istherefore not to be taken in a limiting sense, and the scope of thepresent system is defined only by the appended claims.

Conventional techniques for visualizing blood flow rely on the Dopplerestimation method, which can only provide velocity estimation along theaxial direction. In Doppler imaging, a binary output of the direction ofblood flow (i.e., towards or away from the ultrasound beam) and themagnitude of the velocity in this direction is estimated, which may notprovide sufficient information to a clinician, particularly inapplications where understanding the complex blood flow is critical.Vector flow imaging techniques have emerged to address some of theshortcomings of conventional Doppler. Vector flow imaging (VFI) providesangle-independent multi-directional velocity estimation of blood flowvelocity.

In accordance with examples herein, a system configured for VFI mayinclude, alternative to or in addition to a conventional Dopplerprocessor, a vector flow processor which performs flow estimation over aregion of interest (ROI) to independently obtain the axial andtransverse velocity components of the velocity vector at any givenlocation within the ROI. From the axial and transverse velocityestimates, a magnitude and angle of the velocity at any given point orpixel in the ROI can be obtained and visualized. Vector flow estimationmay be performed in accordance with any known techniques, for exampleusing a transverse oscillation approach, synthetic aperture imaging, orultrafast or continuous imaging, e.g., as described in publications byEvans et al., in “Ultrasonic colour Doppler imaging,” Interface Focus,vol. 1, no. 4, pp. 490-502, August 2011, and by Jensen et al., in“Recent advances in blood flow vector velocity imaging,” 2011 IEEEInternational Ultrasonics Symposium, 2011, pp. 262-271, the contents ofwhich publications are incorporated herein by reference in theirentirety for any purpose. It has been recognized that in providingreal-time vector flow data, VFI presents new challenges due to thewealth of information now obtainable through this new imaging technique.For example, in the case of turbulent flow, for example aroundbifurcations or valves where such rapid changes are often observed, theflow velocity and direction may change rapidly, which can make itdifficult to perceive all clinically relevant details by simplyvisualizing the vector flow field. To perceive clinically relevantchanges in the blood flow, a clinician may need to observe a slow movingcine-loop or study still frames of the vector field, which can be timeconsuming and cumbersome. New solutions for enhancing the visualizingand quantification of vector flow data may be obtained via the systemsand methods described herein, which can improve the clinical utility ofVFI imaging.

FIG. 1 shows a system for visualization and quantification of ultrasoundimaging data in accordance with some examples of the present disclosure.The system includes a display unit 110 and a processor 120. Theprocessor 120 may be communicatively coupled to an ultrasound imagingapparatus 130 to receive ultrasound imaging data, for example ultrasoundimagining data received in real time while a subject is ultrasonicallyscanned. The ultrasound imaging apparatus 130, also referred to hereinas ultrasound scanner, may include an ultrasound array 132 that may behoused in an external or an intravascular probe, and a beamformer 134,which may operate under the control of an imaging controller to directultrasound beams and receive ultrasound echoes from a subject (e.g., apatient) using the ultrasound array 132, which are then beam-formed andtransmitted to one or more processors for further processing and imagegeneration. In some embodiments, the processor 120 and/or the displayunit 110, or components thereof (such as one or more of the processors122, 124, and 126), may be integrated with the ultrasound imagingapparatus 130, which may for example be any of the ultrasound imagingsystem, such as the SPRAQ or the EPIQ ultrasound system, provided byPHILIPS. In some examples, the processor 120 may additionally oralternatively be configured to receive ultrasound imaging data, forexample imaging data from an imaging session performed prior tovisualization and quantification of the data by a clinician, and whichhas been stored in memory (e.g., memory storage device of a picturearchiving and communication system (PACS)) for later access by theprocessor 120.

The processor 120 may be configured to generate ultrasound images 112for display on the display unit 110. To that end, the processor mayinclude a B-mode processor 122 configured to generate B-mode images anda Doppler processor 124 configured to generate Doppler images (e.g.,color-flow Doppler, spectral Doppler, and power Doppler such as ColorPower Angio (CPA) images). In some examples, images may be displayed asoverlays of imaging data obtained from multiple imaging modes. Forexample in duplex (e.g., B-mode/Doppler) imaging, a gray-scale image ofthe anatomy (i.e., a B-mode image) may be overplayed with color-flowDoppler data to provide, for example, a color-flow Doppler image. Inaccordance with the present disclosure, the processor 120 may include avector flow processor 126 configured to generate vector flow imagingdata based on the ultrasound imaging data (e.g., real-time or pre-storedimaging data), which data may be overlaid on background D-mode imagessimilar to B-mode/Doppler duplex imaging. In some embodiments, thesystem may include only a vector flow processor, while the B-mode imagedata and/or images and Doppler image data and/or images are generated byan ultrasound scanner and stored in memory (e.g., PACS), for access andoverlay with the vector flow imaging data generated by the visualizationsystem. In other embodiments, B-mode, Doppler, and vector flow imagingdata is generated in real time and visualization and quantification maybe performed in real time (i.e., during the acquisition of theultrasound imaging data). In some embodiments, the functionality of oneor more of the processors (e.g., B-mode processor 122, Doppler processor124, and vector flow processor 126) of system 100 may be integrated intoa single or a fewer number of processors such as a specially programmedCPU or GPU operable to perform the functions of these processordescribed herein.

Information extracted from the vector flow imaging data may be renderedon the display unit 110 in the form of vector flow visualization data(e.g., a 2D or a 3D vector map) and/or spatiotemporal visualizationdata. The vector flow visualization data provides a graphicalrepresentation of the vector field, which may be in the form of a 2D ora 3D vector map. The spatiotemporal visualization data provides agraphical representation of quantitative information about one or morevelocity vectors visualized as a function of time. For example,spatiotemporal visualization data may be graphically represented usingvarious plots or graphs, such as graphs of the magnitude or angle of avelocity vector any given point (e.g., a user-selected point) as afunction of time, or as dynamically updated graph displaying thedirection of a single or a plurality of velocity vectors isolated fromthe larger vector field, e.g., responsive to user input. In someexamples, the quantification may be performed for a small selectedregion which may include a plurality of points or pixels. In suchexamples, the spatiotemporal visualization data may include a pluralityof traces (i.e., a trace for each of the set of points or pixels in theselected region), and the plurality of traces may be presented in asingle graph or in separate graphs. In yet further embodiments, thespatiotemporal information may be averaged over the plurality of pointsof the selected region and a single graph of the averaged values may beprovided on the display. The vector flow visualization data andspatiotemporal visualization data may be displayed concurrently (e.g.,side-by-side, or as an overlay) with imaging data from other modes, forexample as an overlay or a side-by-side display with B-mode image data.Thus, in accordance with the examples herein, the processor 120 isconfigured to cause the display unit 110 to concurrently display atleast two types of imaging data 112-1 and 112-2, as will be furtherdescribed.

Vector flow imaging data generated by the vector flow processor 126 maybe visualized using any suitable visualization technique, such asfixed-arrow based, free-arrow based, and pathlet-based visualization.For fixed-arrow-based visualization, the magnitude of flow velocity istypically encoded as color intensity, and is proportional to the lengthof the arrow. The direction of flow velocity is typically shown both bythe arrow and color. The tail of the arrow is fixed in space. Forfree-arrow-based visualization, free arrows are used to dynamicallytrack the blood flow. The magnitude of flow velocity is typically colorencoded, and is proportional to the length of the arrow. The directionof flow velocity is indicated by the arrow.

In the context of VFI, a streamline may be defined as a family of curvesthat are instantaneously tangent to the velocity vector of the flow, anda pathline can be defined as a family of trajectories that the flowparticles would faithfully follow during flow. For pathlets-basedvisualization, dynamic curve tracing of the flow trajectory is achievedby curved pathlets. Pathlets can be seen as the short, frontal segmentsor parts of the pathlines, that start to fade out when distance from thetip exceeds a given threshold, which is defined as the pathlet length.The magnitude of flow velocity is color encoded, and is proportional tothe length of the pathlets. The direction of flow velocity is indicatedby the moving direction of pathlets. Overall, among the threevisualization methods, pathlet-based visualization may be deemed themost intuitive method with potential to replace the other visualizationmethods for VFI.

FIG. 2 shows an example of a system 200 for visualization andquantification of vector flow data. The system 200 in FIG. 2 may utilizepathlet-based visualization or any other suitable technique to visualizethe vector field. The system 200 may include a vector flow processor203, which is coupled to a source of ultrasound imaging data. Forexample, the ultrasound imaging data 202 may be received (e.g., in realtime) from an ultrasound imaging apparatus (e.g., ultrasound scanner)responsive to ultrasonically scanning a region of interest 201. In someexamples, the vector flow processor 203 may be communicatively coupledto a B-mode processor 205. The B-mode processor may also be coupled tothe source of ultrasound imaging data to generate background grayscaleimages for display with the vector flow data. The vector flow processor203 may additionally or alternatively be coupled to a data storagedevice 207 (e.g., memory of an ultrasound imaging apparatus or PACS),which may store ultrasound imaging data and/or B-mode images.

In accordance with the examples herein, the vector flow processor 203may be configured to generate a graphical representation of a vectorfield representative of blood flow in a region of interest (ROI). Forexample, the vector flow processor 203 may include a velocity vectorestimator 210, a visualization processor 220, and a frame buffer 230(also referred to as VFI memory 230). The frame buffer 230 may storeframes of data used at various stages of the VFI process. For example,the frame buffer 230 may store frames of vector field data generated bythe velocity vector estimator 210. The frame buffer 230 may store framesof visualization data before it is overlaid on background images and/orcombined with other graphical information (e.g., annotations) fordisplay. As described herein, velocity vector estimation may beperformed by the velocity vector estimator 210 in accordance with anysuitable technique, several of which have been developed and can be usedherein, to obtain a velocity vector field for the ROI. In some examples,ultrafast Doppler imaging (e.g., using plane wave imaging) may beperformed at sufficiently high pulse repetition frequency (PRF) in orderto obtain sufficiently high frame rates to enable velocity vectorestimation. At the end of the vector estimation process, which isoutside of the scope of this disclosure as it may be implemented usingknown vector extraction techniques, a vector field 215 for each imageframe may be generated and passed to the frame buffer 230. The vectorfield frame data 232 may be stored in the buffer 230 until it isaccessed by the visualization processor 220 for generating vector flowimages 226.

In accordance with the examples herein, the vector flow processor 203may be configured to cause a display unit of the system (252) to displayan ultrasound image of the graphical representation of the vector field(e.g., vector map) overlaid on a B-mode image of the ROI. The vectorflow processor 203 may receive an indication of a selected region withinthe vector field, for example responsive to user input 253 received viathe control panel 254 of user interface 250. The vector flow processor203 may be configured to then update the ultrasound image to displayspatiotemporal information about the vector field at the selectedregion. For example, the visualization processor 220 may include avector map processor 222 configured to produce vector flow visualizationdata 226-1 (e.g., a vector map), and may further include aquantification processor 224 configured to generate spatiotemporalvisualization data 226-2 (e.g., a graph of a vector quantity dynamicallyupdated over time). In a similar manner to traditional duplex color-flowor power Doppler images, background B-mode images 206 (e.g., real-timeor stored B-mode images) may be overlaid with the vector flowvisualization data 226-1 (e.g., the vector map) and displayed in aduplex B-mode/VFI mode. Spatiotemporal visualization data 226-2 may beprovided concurrently with the display of the duplex B-mode/VFI modeimage.

As will be further described, spatiotemporal information may be providedat one or more selected points in the vector field. Points forquantification may be selected by the user. For example, a selectedregion that includes a single point may be selected by a single click atany desired location within the displayed vector field. Upon theselection of a region that includes a single point for quantification, asingle trace would be provided on the display that corresponds toselected point. Additional points may be subsequently selected by theuser in the same manner, e.g., by clicking on any other point within thedisplayed vector field, responsive to which additional tracescorresponding to the additional selected points would be added to thespatiotemporal display. A selected region that includes a plurality ofpoints may be selected by the user by placing the cursor at any desiredlocation within the displayed vector field and dragging the cursor todefine the desired grouping of pixels to be included in the selectedregion. Upon selection of a region of multiple points, either a singletrace averaging the velocity information over the region would bedisplayed or a plurality of traces, one for each point in the selectedregion, may be provided in the spatiotemporal display.

Alternatively or additionally, points may be automatically selected bythe system (e.g., by the vector flow processor 203), such as based on apre-set default for a given clinical application or based on assessmentof the vector flow data. For example, in the case of the latter, thevector flow processor 203 may sample a set of consecutive frames ofvector flow data to identify one or more locations in the vector fieldexhibiting turbulence and select a point at the location of maximumturbulence. In other examples, such as when imaging a relatively laminarflow through a vessel, the system may default the selected point at alocation along the centerline of the vessel, which may be identifiedusing image processing techniques (e.g., segmentation). In otherembodiments, image processing techniques may be used to identifyclinically relevant landmarks of the ROI being imaged and locate theselected point(s) at one or more of the clinically relevant landmarks.The default selected point may be used to initially providespatiotemporal information until the user moves/removes the defaultpoint and/or selects another point. In some embodiments, spatiotemporalinformation may be displayed only after the user has selected a point inthe vector field (e.g., after the visualization of the vector field hasbeen provided to the user). In such embodiments, the ultrasound imagedisplaying the vector flow visualization data may be updated once theuser selects a point, to provide the spatiotemporal informationconcurrently with the continued display of the vector flow visualizationdata, both of which may be updated in real time. In some embodiments inwhich spatiotemporal information is not initially provided, place holdergraphical elements (e.g., a blank graph window displaying the axes orother information, such as labels, about the information be provided)may be provided on the display, and the place holder graphical elementsmay only being to update with spatiotemporal information after the userhas selected the desired point for quantification.

In further embodiments, the spatiotemporal information may be an amountof blood flow or quasi- (i.e., 2D) or volumetric flow rate through thevessel, which may be estimated from the vector flow data. For example,the system may receive an indication of a location along the length ofthe vessel and define a flow boundary (e.g., a line in the case of 2D orarea in the case of 3D visualization). In other embodiments, the systemmay automatically define the boundary at a location generally centeredalong the length of the vessel or at a location of highest turbulencewithin the imaged ROI. The boundary may be defined so that it isgenerally perpendicular to the lumen at the selected location or it maybe generally aligned with the axial direction. The system may thenestimate the amount of flow that passes through the boundary and plotthis estimate as a function of time. In some embodiments, the system mayprovide a spatiotemporal display of vector flow information across aboundary, for example by plotting the values of the magnitude of thevelocity at each point along the boundary (this information can beplotted on the y axis), as a function of time. Additionally, thisspatiotemporal display may be color-coded to also provide the angle ofthe flow at each spatial location across the boundary. Otherspatiotemporal displays may also be provided to visualize the fluxacross or along the vessel which may aid in diagnosis of vasculardisease (e.g., plaque severity and/or risk of plaque rupture).

In some embodiments, the processor (e.g., vector flow processor 203) ofthe visualization and quantification system (e.g., system 200) may beconfigured to generate a pathlet-based representation of the vectorfield. FIGS. 3-5 illustrate examples of pathlet-based graphicalrepresentations of a vector field in accordance with some examples.While an example VFI technique using a pathlet-based visualization isdescribed with reference to FIGS. 3-5, it will be understood that thevisualization and quantification systems and methods described hereinare not limited to implementations using pathlet-based visualization andcan similarly be utilized with other vector flow imaging visualizationtechniques. Other VFI techniques, including but not limited tofixed-arrow based or free-arrow based techniques, may also be used.

The vector flow visualization data 226-1 in the case of pathlet-basedvisualization may be provided in the form of a vector map 301, whichinclude two components, as illustrated in FIG. 3: 1) a flow mask layer305 delineating the flow region in a primary color (e.g., dark red oranother) with a desired baseline transparency, for example 50%, so as tonot completely obfuscate the background image (B-mode image 206), and 2)a vector field layer 307 illustrating the trajectories 309 of flowparticles, which in this example are shown using pathlets.

In some embodiments, the flow region for which vector flow estimates areobtained and thus vector flow visualization performed may beuser-defined, such as responsive to a user selection of a sub-regionwithin the imaged ROI. In such embodiments, the size and shape of theflow mask layer 305 and correspondingly the vector field layer 307 areuser-defined. This region selected by the user for vector flowvisualization is not to be confused with the subsequently selectedregion for quantification, which may include a single or a subset ofpoints within the vector flow visualization region. In otherembodiments, the flow region for which vector flow visualization isperformed may be automatically defined by the system, e.g., exampleusing image segmentation or other suitable image processing techniquessuch as to identify the walls of the vessel. In such embodiments, thesystem (e.g., vector flow processor 203) may define the flow region toinclude the area inside an imaged vessel, and correspondingly a flowmask layer 305 and vector field layer 307 are produced for allpoints/pixels within the system-defined flow region.

In yet further embodiments, the flow region for which vector flowvisualization is performed may be automatically defined by the system(e.g., vector flow processor 203) based on available blood flow velocitydata (i.e., based on points/pixels in the image which are associatedwith detected blood flow in any given frame). In such embodiments, thesystem may generate a flow mask layer 305 and corresponding vector fieldlayer 307 for the system-defined flow region by including within theflow region all points/pixies in the image for which velocity estimatesare available in any given frame. In such embodiments, the system (e.g.,vector flow processor 203) may automatically update the vector flowimage to reflect temporal variations in the blood flow velocity data.That is, as blood flow varies from frame to frame (e.g., responsive tothe different phases of the cardiac cycle), the flow mask layer 305corresponding vector field layer 307 may be dynamically updated fromframe to frame to reflect this variation. Thus, the displayed vectorfield map may have a different shape or size in different frames (seee.g., FIGS. 6A and 6B). A combination of any of these or other suitabletechniques may be used to define the flow region.

As described, pathlets for visualizing the vector field may be generatedand updated in real-time (e.g., a frame of vector flow visualizationdata may be generated for each frame of image data) and overlaid on theflow mask to produce a vector flow image, which is then overlaid ontothe corresponding B-mode image frame for display (e.g., on display unit252). In this manner, e.g., by updating the pathlets in real time, thevector flow image may provide a visual cue of the movement of thetracked particles (e.g., blood flow). Each pathlet begins fading outwhen a distance from the tip exceeds a given threshold. That is, a headof the pathlet is always more opaque than the tail, enabling easieridentification of the moving direction (i.e., flow direction) of thepathlet, even in a static image, without the inclusion of arrows thatmay clutter the display. Additionally, the pathlets may be color-codedand/or the pathlet length may be proportional to the velocity magnitude,both of these features helping the user more easily visualize thevelocity magnitudes.

FIG. 4 shows partial magnified images of two consecutive frames 401(i.e., frames N and N+1) of a pathlet-based vector map, which includespathlets 403-1 and 403-2. The pathlets in the vector map, as well as thevector map generally, may be defined using several parameters, includinglength (alternativley, or additional and optionally, duration), width,and density of pathlets, generation rate of new pathlets (oralternatively vanish rate of old pathlets), color range for mapping ofpathlets, display frame rate, and transparency and color of the flowmask, any of which parameters may be user-configurable (before or duringimaging) to obtain a desired visualization effect without compromisingthe diagnostic performance of the system.

To generate the pathlets, initially a number of frames of the vectorfield data are saved and pathelts are generated for each frame, forexample by interpolating the trajectory of tracked particles over thenumber of initial frames. For each subsequent frame, the pathelts areupdated based on the velocity vector data associated with the subsequentframes. For example, in FIGS. 4A and 4B, the pathlets 403-1 and 403-2illustrate the frontal portion of the trajectories of two tracked flowparticles, the last several locations of one of which are shown by thepoints N+1, N, N−1, N−2, N−3, N−4, and N−5 which for illustration are solabeled to indicate the frame with which they are associated. The frontmost point in each frame indicates the estimated location of the trackedparticle in that frame. The front most point of the pathlet in eachframe (e.g., point N in frame N and point N+1 in frame N+1) is referredto as the head 405 of the pathlet. The pathlets may be updated everyframe to reflect the movement of the particle to a new location and thusthis movement may be visualized on the display by the changing locationof the head 405 of the pathlet in each updated frame. The new locationof the tracked particle and thus the head 405 is calculated using theangle-independent velocity estimates (i.e., the axial and lateralvelocity components in the case of a 2D map or the axial, lateral andelevational velocity components in the case of a 3D map), which can beobtained in real-time or prior to the visualization. For example theaxial displacement of the tracked particle may be calculated as Vz/fFRand the lateral displacement of the tracked particle may be calculatedas Vx/fFR, where Vx is the lateral velocity (m/s), Vz is the axialvelocity (m/s) of the head, and fFR is the tracking frame rate (Hz). Acontinuous and smooth pathlet is generated by interpolation (linear orcubic) of these discrete dots, and then displayed as an aliasing-freeline.

Overtime, the aft end of a particle's trajectory fades, e.g., to reduceclutter on the display, and only the frontal portion of the trajectoryis shown on the display. The aft end of the displayed pathlet isreferred to as the tail 407 of the pathlet. The pathlets (e.g., pathlets403-1 and 403-2) may be color-coded based on the velocity magnitude atdifferent locations (i.e., each segment 409 between the location of theparticle in a previous frame and the location of the particle in the hecurrent frame may reflect the estimated velocity magnitude of theparticle in the current frame). A color map key 311 (see FIG. 3) for thevector map may be displayed concurrently with the vector flow image. Inaddition to color-coding, the transparency of each pathlet may belinearly distributed with the highest opacity at the head 405 anddecreasing to lowest opacity at the tail 407. The transparencydistribution may also be updated at each frame. That is, when a newsegment 409 is added in a new frame, the transparency may be linearlyre-distributed with highest opacity (e.g., 50% or other) at the head 405and decreasing to e.g., 100% transparency at the tail 407. Thetransparency may be linearly distributed, such as on a per pixel basisalong the length of the pathlet or on a per segment basis. In thismanner, the transparency distribution of the pathless may enhance theease in identifying the direction of flow, even in a static image.

As previously described, each pathlet may have a maximum length, whichmay be pre-set or user defined. As the pathlet is update frame to frame,it grows in length in each frame due to the addition of a new segment atthe head while maintaining the same tail. Once the pathlet reaches itsmaximum length (e.g., after being updated certain number of frames), itmaintains a length shorter than the maximum length by deletion of theoldest location of the particle and correspondingly the aft most segment(also referred to as tail segment). If the pathlet is further defined byduration, with each frame in which the pathlet is updated, a lifetimevariable of the pathlet is incremented until the lifetime variable of agiven pathlet reaches the maximum lifetime, at which point the pathletis removed from the display. For example, alternatively or additionally,each pathlet may have a lifetime, which can be defined using an integervariable randomly generated between the maximum pathlet length and themaximum lifetime when the pathlet is created. The age of a pathlet isdecrease by one for each frame (e.g., every time the pathlet isupdated). Once the age reaches zero, the pathlet is deleted from thevector map. A new pathlet may be created at the same time or in adifferent frame with another random lifetime assigned to it. With thislifetime feature, a balanced spatial distribution of pathlets may bemaintained.

The pathlets may be updated using an iterative process for anysubsequent frame. When the inputs (e.g., array variables includinglateral position (x), axial position (z), lateral velocity V_(x), andaxial velocity (V_(z)), and two integer variables including “head ofpathlet”, and “lifetime of the pathlet”) are received by the vector flowprocessor, the locations and lifetimes of the pathlets are examined. Ifa pathlet is located within the flow region, and its lifetime is greaterthan zero, it is defined as an active pathlet. If the pathlet movesoutside of the flow region, or its lifetime is zero, it is defined as aninactive pathlet. For any active pathlets, the new head is computedbased on the velocity maps, and the lifetime decreased by one. Anyinactive pathlets are deleted from the display. An inactive pathlet maybe replaced with a new pathlet for example, by randomly generating a newlocation and a new lifetime for the replacement pathlet. After the datastructure for each pathlet is updated, the vector flow processor maygenerate (e.g., by interpolation) a smooth and continuous aliasing-freeline to visualize the pathlets. The color of the line corresponding toeach pathlet is coded based on the velocity magnitudes and thetransparency of the color-coded pathlet is distributed along its length(i.e., from the new head to new tail of the pathlet) for rendering onthe display.

Referring back to FIG. 2, the system may include a display unit 252,which may be part of a machine-user interface 250, which may include auser control unit 842 (e.g., a control panel). In some embodiments, theuser control unit and display unit 252 are integrated in atouch-sensitive display which is operable to both display the images 251and receive user inputs. Commands 253 responsive to the user inputs maybe transmitted to the vector flow processor 203 for example forcontrolling the generation of spatiotemporal image data and/or otheraspects of the display.

Referring now also to FIGS. 5 and 6, examples of ultrasound imagesgenerated for display by a visualization and quantification system ofthe present disclosure, for example system 200. The system may beconfigured to display an ultrasound image including at least two imagecomponents, one of which includes vector flow visualization data, theother including spatiotemporal data. In some examples, multiplespatiotemporal image components may be included in the ultrasound imageto provide quantitative information about a plurality of differentparameters or to visualize the same parameter in different ways.

FIG. 5 shows a screen capture 501 from a display unit (e.g. display 252)of a system built in accordance with the examples herein. The screencapture includes an ultrasound image 510 of a blood vessel. The image510 includes a graphical representation of a vector field (in window Aof the display) and spatiotemporal information associated with thevector field (in windows B and C of the display). The labels A, B, and Cin the image in FIG. 5 are provided solely for ease of illustration andto facilitate understanding of the disclosure and may not be present inembodiments of the invention. Window A in FIG. 5 illustrated a firstimage element 512 that includes the graphical representation of thevector field, in this case a pathlet-based vector map 513. The vectormap 513 may be generated and updated (e.g., in real time) in accordancewith the examples herein (e.g., as described with reference to FIGS. 3and 4. The vector map 513 is overlaid on a background B-mode image 515of the imaged ROI. Windows B and C in FIG. 5 illustrate additionalelements 514 and 516 of the image, specifically image elements thatprovide quantitative information about one or more points in the vectorfield visualized in Window A. Specifically, window B includes a graph ofthe magnitude of the velocity vector as a function of time for each ofthe selected points. In this illustrated example, two points have beenselected (e.g., selected points 522 and 523) and two curves (temporaltraces 532 and 533 corresponding to the points 522 and 523,respectively) are shown in window B. Each of the curves 532 and 533traces the velocity magnitude (in cm/s, as shown on the y-axis) at eachof the selected points as a function of time (in seconds, as shown onthe x-axis). The blood flow through the vessel in this illustratedexample is relatively laminar (i.e., without much variation in flowdirection across the lumen) and exhibits relatively constant velocitymagnitude over the displayed time sequence aside from expectedvariations in velocity magnitude due to the cardiac cycle (e.g., asevidence by an increase of flow velocity following systole around 0.4seconds in the sequence). As will be further illustrated, more turbulentblood flow may be observed in other vessels, such as near the carotidbifurcation (see e.g., FIGS. 6A and 6B) and/or in the presence of plaquein a vessel. The visualization tools described herein may beparticularly useful in extracting clinically useful quantitativeinformation about the blood flow in such cases.

In use, a system for visualizing and quantifying blood flow according tothe present disclosure may operate as follows. Once echo amplitudedetection, e.g., for generating B-mode images, and velocity estimation,e.g., to generating vector flow information, have been performed, thesystem may render an ultrasound image, such as the image 510 in FIG. 5.This may occur in real-time (i.e., while imagining the subject) or afteracquisition of the imaging data. In some embodiments, initially (e.g.,prior to receiving user input selecting at least one point in the vectorfield), the image 510 may include only the image element 512. In otherembodiments, placeholder elements 514 and 516, which may not provide anyspatiotemporal information, may be included and only populated with thetraces after the selection of the region (e.g., points) to bequantified. In yet further examples, both the vector flow andspatiotemporal information may be initially provided (e.g., in instancesin which the system auto-selects a region for quantification).

In a subsequent step, the system may receive an indication of a selectedregion (e.g., a single point or a cluster of points selected responsivee.g., to a single click or a dragging of the pointer within the vectorflow display in image 510). The vector flow display may be updating inreal-time as the user makes the selection, or the user may freeze thedisplay and make the selection in the frozen frame. Once a selection ismade, the vector flow image (in window A) may automatically unfreeze, ifpreviously frozen, and the system may add or begin to update thespatiotemporal elements of the image (e.g., elements 514 and 516 shownin windows B and C). The vector flow image as well as the spatiotemporalimages may continue to update synchronously until the end of thetemporal sequence, and in the case of real-time visualization, theupdating occurs synchronously in all windows in real-time as data isbeing acquired by the system.

A variety of graphical elements may be used to provide thespatiotemporal displays. For example, the system may be configured tocause the displaying of a graph, which traces the changing velocitymagnitude over time (e.g., as shown in window B). In other embodiments,instead of the magnitude, the angle of the velocity vector may bedisplayed as a function of time in window B or an additional graph maybe provided to concurrently display the angle as a function of time. Insome embodiments, the angle may be visually represented using a graph ofthe type shown in window C. In the graph in window C, the direction offlow at each of the selected points 522 and 523 are visualized by therespective arrows 542, 543, which are defined by the axial component ofthe velocity vector (y axis) versus the transverse or lateral componentof the velocity vector (x axis). As with any other spatiotemporal imageelement, the graphs in window C is updated synchronously with the otherelements of the image (e.g., windows A and B) to provide a dynamicvisual representation of a single or a small number of blood flowvelocity vectors that pass through the selected points.

In some examples, the system may be configured to receive as input aselection of a plurality of points, which may be received concurrently(e.g., as a selection of a small sub-region or cluster of points) orsequentially (e.g., one point selected after another), and thespatiotemporal displays may be updated responsive to any new selectionmade. For example, as shown in FIG. 5, the user may also select a secondpoint 523 is selected by the user following the selection of point 522.Upon selection of an additional point, the system adds additional tracesto the spatiotemporal displays to provide quantitative information aboutthe additional selected points. Alternatively or additionally, thesystem may be configured to receive an indication of a selected regionwhich includes a cluster of points or pixel (e.g., by dragging thecursor within the vector field to define the selected region), whichcase multiple traces for each point in the region may be concurrentlydisplayed or a single averaging trace may be provided depending on theparticular pre-set or user configuration of the system.

FIGS. 6A and 6B show additional screen captures 501′ and 501″ from adisplay unit (e.g. display 252) of a system built in accordance with theexamples herein. These screen captures illustrate ultrasound images ofthe carotid artery and visualizations of the blood flow therethrough atvarious phases of the cardiac cycle. Similar to the image in FIG. 5, theultrasound images 510 in each of the screen captures in FIGS. 6A and 6Binclude a plurality of image elements (e.g., elements 512, 514, and516), which may provide a graphical representation of a vector field(e.g., a vector flow image in element 512) and spatiotemporalinformation associated with the vector field (e.g., traces 532′ and 533′of the velocity magnitude as a function of time and associated velocityangles represented by arrows 542′ and 543′ at the respective points 522′and 533′). Unlike the relatively laminar flow in FIG. 5 the flow at thecarotid bulb is more turbulent as seen in the images in FIGS. 6A and 6B,and the variability in velocity magnitude and direction can be moreeasily perceived and quantified at specific selected point using thetechniques described herein.

FIGS. 7A-7C illustrated different VFI imaging techniques which can beutilized for vector flow visualization by the systems described herein.While two dimensional (2D) vector fields are shown in the variousillustrated examples herein, it will be understood that in someembodiments, the processor (e.g., vector flow processor 203) of thevisualization and quantification system (e.g., system 200) may beconfigured to also estimate a third velocity component (e.g.,elevational component) of the blood flow velocity in the ROI in additionto the axial and lateral components in order to produce a graphicalrepresentation of a three dimensional (3D) vector field (e.g., a 3Dvector map). The 3D vector map may be overlaid on a 3D image of avolumetric ROI to provide a 3D rendering of the ultrasound data. Inaccordance with known techniques, slices may be taken through the imagedvolumetric region and vector flow visualization and quantification maybe performed at the selected image or slice plane and in some casesoverlaid on the volume at the slice plane.

As described herein, one or more of the components of the system may bepart of a stand-alone visualization system communicatively coupled to asource of ultrasonic imaging data, which may be pre-stored or receivedin real-time. For example, at least one of the display and the processormay be part of a workstation separate from the ultrasound imagineapparatus, and may be configured to generate the ultrasound image fromreal-time or pre-stored ultrasound imagining data. In further examples,the system for visualization and quantification according to the presentdisclosure may be integrated with an ultrasound imagining systemconfigured to acquire the ultrasound echoes. For example, ultrasoundimaging apparatus may be provided by an ultrasound diagnostic systemincluding the display and the processor, wherein the ultrasounddiagnostic system is configured to generate and update the ultrasoundimage in real time while ultrasonically imaging the subject.

FIG. 8 shows a block diagram of an ultrasound system 800 according tothe present disclosure. Some or all of the components of system 800 maybe used to implement components of any one of the visualization andquantification systems described herein, for example the ultrasoundimaging apparatus of FIG. 1. The ultrasound system 800 may include anultrasound transducer array. In the illustrated example, the ultrasoundtransducer array 814 is provided in a probe 812. In some examples, thearray 814 may be implemented using a plurality of patches, eachcomprising a sub-array of transducer elements and the array 814 may beconfigured to be conformably placed against the subject to be imaged.The array 814 is operable to transmit ultrasound toward a region ofinterest and to receive echoes for imaging the region of interest (ROI).A variety of transducer arrays may be used, e.g., linear arrays, curvedarrays, or phased arrays. The array 814 may include, for example, a twodimensional array of transducer elements capable of scanning in bothelevation and azimuth dimensions for 2D and/or 3D imaging.

The array 814 may be coupled to a microbeamformer, which may be locatedin the probe or in an ultrasound system base (e.g., in a cart-basedsystem such as the SPARQ or EPIQ ultrasound system provided by Philips.The microbeamformer may control the transmission and reception ofsignals by the array. The array 814 may be coupled to the ultrasoundsystem base via the microbeamformer 816, which may be coupled (via awired or wireless connection) to a transmit/receive (T/R) switch 818typically located in the base. The T/R switch 818 may be configured toswitch between transmission and reception, e.g., to protect the mainbeamformer 822 from high energy transmit signals. In some embodiments,the functionality of the T/R switch 818 and other elements in the systemmay be incorporated within the probe, such as a probe operable to coupleto a portable system, such as the LUMIFY system provided by PHILIPS. Theprobe 812 may be communicatively coupled to the base using a wired orwireless connection.

The transmission of ultrasonic pulses from the array 814 may be directedby the transmit controller 820 coupled to the T/R switch 818 and thebeamformer 822, which may receive input from the user's operation of auser interface 824. The user interface 824 may include one or more inputdevices such as a control panel 842, which may include one or moremechanical controls (e.g., buttons, encoders, etc.), touch sensitivecontrols (e.g., a trackpad, a touchscreen, or the like), and other knowninput devices. Another function which may be controlled by the transmitcontroller 820 is the direction in which beams are steered. Beams may besteered straight ahead from (orthogonal to) the transmission side of thearray 814, or at different angles for a wider field of view. Thebeamformer 822 may combine partially beamformed signals from groups oftransducer elements of the individual patches into a fully beamformedsignal. The beamformed signals may be coupled to a signal processor 826.The system 800 may include one or more processors (e.g., data and imageprocessing components collectively referred to as 850) for generatingultrasound image data responsive to the echoes detected by the array814, which may be provided in a system base. The processing circuitrymay be implemented in software and hardware components including one ormore CPUs, GPUs, and/or ASICs specially configured to perform thefunctions described herein for generating ultrasound images andproviding a user interface for display of the ultrasound images.

For example, the system 800 may include a signal processor 826 which isconfigured to process the received echo signals in various ways, such asby bandpass filtering, decimation, I and Q component separation, andharmonic signal separation. The signal processor 826 may also performadditional signal enhancement such as speckle reduction, signalcompounding, and noise elimination. The processed signals may be coupledto a B-mode processor 828 for producing B-mode image data. The B-modeprocessor can employ amplitude detection for the imaging of structuresin the body. The signals produced by the B-mode processor 828 may becoupled to a scan converter 830 and a multiplanar reformatter 832. Thescan converter 830 may be configured to arrange the echo signals in thespatial relationship from which they were received in a desired imageformat. For instance, the scan converter 830 may arrange the echo signalinto a two dimensional (2D) sector-shaped format, or a pyramidal orotherwise shaped three dimensional (3D) format. The multiplanarreformatter 832 can convert echoes which are received from points in acommon plane in a volumetric region of the body into an ultrasonic image(e.g., a B-mode image) of that plane, for example as described in U.S.Pat. No. 6,443,896 (Detmer). A volume renderer 834 may generate an imageof the 3D dataset as viewed from a given reference point, e.g., asdescribed in U.S. Pat. No. 6,530,885 (Entrekin et al.).

Additionally or optionally, signals from the signal processor 826 may becoupled to a Doppler processor 852, which may be configured to estimatethe Doppler shift and generate Doppler image data. The Doppler imagedata may include colorflow data which may be overlaid with B-mode (orgrayscale) image data for displaying a conventional duplexB-mode/Doppler image. In some examples, the Doppler processor 826 mayinclude a Doppler estimator such as an auto-correlator, in whichvelocity (Doppler frequency) estimation is based on the argument of thelag-one autocorrelation function and Doppler power estimation is basedon the magnitude of the lag-zero autocorrelation function. Motion canalso be estimated by known phase-domain (for example, parametricfrequency estimators such as MUSIC, ESPRIT, etc.) or time-domain (forexample, cross-correlation) signal processing techniques. Otherestimators related to the temporal or spatial distributions of velocitysuch as estimators of acceleration or temporal and/or spatial velocityderivatives can be used instead of or in addition to velocityestimators. In some examples, the velocity and power estimates mayundergo threshold detection to reduce noise, as well as segmentation andpost-processing such as filling and smoothing. The velocity and powerestimates may then be mapped to a desired range of display colors inaccordance with a color map. The color data, also referred to as Dopplerimage data, may then be coupled the scan converter 830 where the Dopplerimage data is converted to the desired image format and overlaid on theB-mode image of the tissue structure containing the blood flow to form acolor Doppler image.

In accordance with the principles of the present disclosure, the system800 may include vector flow processing components including a velocityvector estimator 854 and a VFI renderer 856. The velocity vectorestimator may receive signals from the signal processor 826 and performvelocity estimation to obtain the angle-independent velocity vectordata, as described herein. The velocity vector data (e.g., vector flowfield) may be passed to a VFI renderer 856 for generating graphicalrepresentations of the velocity vector data, including vector fieldvisualization data and spatiotemporal data. Output (e.g., images) fromthe scan converter 830, the multiplanar reformatter 832, the volumerenderer 34, and/or the VFI renderer 856 may be coupled to an imageprocessor 836 for further enhancement, buffering and temporary storagebefore being displayed on an image display 854. The system may include agraphics processor 840, which may generate graphic overlays for displaywith the images. These graphic overlays may contain, e.g., standardidentifying information such as patient name, date and time of theimage, imaging parameters, and other annotations. For these purposes,the graphics processor may be configured to receive input from the userinterface 824, such as a typed patient name. Although shown as separatecomponents, the functionality of any of the processors herein (e.g., thevelocity vector estimator 854 and/or the VFI renderer 856) may beincorporated into other processors (e.g., image processor 836 or volumerenderer 834) resulting in a single or fewer number of discreteprocessing units. Furthermore, while processing of the echo signals,e.g., for purposes of generating B-mode images or Doppler images arediscussed with reference to a B-mode processor and a Doppler processor,it will be understood that the functions of these processors may beintegrated into a single processor, which may be combined with thefunctionality of the vector flow processing components.

In various embodiments where components, systems and/or methods areimplemented using a programmable device, such as a computer-based systemor programmable logic, it should be appreciated that the above-describedsystems and methods can be implemented using any of various known orlater developed programming languages, such as “C”, “C++”, “FORTRAN”,“Pascal”, “VHDL” and the like. Accordingly, various storage media, suchas magnetic computer disks, optical disks, electronic memories and thelike, can be prepared that can contain information that can direct adevice, such as a computer, to implement the above-described systemsand/or methods. Once an appropriate device has access to the informationand programs contained on the storage media, the storage media canprovide the information and programs to the device, thus enabling thedevice to perform functions of the systems and/or methods describedherein. For example, if a computer disk containing appropriatematerials, such as a source file, an object file, an executable file orthe like, were provided to a computer, the computer could receive theinformation, appropriately configure itself and perform the functions ofthe various systems and methods outlined in the diagrams and flowchartsabove to implement the various functions. That is, the computer couldreceive various portions of information from the disk relating todifferent elements of the above-described systems and/or methods,implement the individual systems and/or methods and coordinate thefunctions of the individual systems and/or methods described above.

In view of this disclosure it is noted that the various methods anddevices described herein can be implemented in hardware, software andfirmware. Further, the various methods and parameters are included byway of example only and not in any limiting sense. In view of thisdisclosure, those of ordinary skill in the art can implement the presentteachings in determining their own techniques and needed equipment toaffect these techniques, while remaining within the scope of theinvention. The functionality of one or more of the processors describedherein may be incorporated into a fewer number or a single processingunit (e.g., one or more CPUs or GPU) and may be implemented usingapplication specific integrated circuits (ASICs) or general purposeprocessing circuits which are programmed responsive to executableinstruction to perform the functions described herein.

Although the present system may have been described with particularreference to an ultrasound imaging system, it is also envisioned thatthe present system can be extended to other medical imaging systemswhere one or more images are obtained in a systematic manner.Accordingly, the present system may be used to obtain and/or recordimage information related to, but not limited to renal, testicular,breast, ovarian, uterine, thyroid, hepatic, lung, musculoskeletal,splenic, cardiac, arterial and vascular systems, as well as otherimaging applications related to ultrasound-guided interventions.Further, the present system may also include one or more programs whichmay be used with conventional imaging systems so that they may providefeatures and advantages of the present system. Certain additionaladvantages and features of this disclosure may be apparent to thoseskilled in the art upon studying the disclosure, or may be experiencedby persons employing the novel system and method of the presentdisclosure. Another advantage of the present systems and method may bethat conventional medical image systems can be easily upgraded toincorporate the features and advantages of the present systems, devices,and methods.

Of course, it is to be appreciated that any one of the examples,embodiments or processes described herein may be combined with one ormore other examples, embodiments and/or processes or be separated and/orperformed amongst separate devices or device portions in accordance withthe present systems, devices and methods.

Finally, the above-discussion is intended to be merely illustrative ofthe present system and should not be construed as limiting the appendedclaims to any particular embodiment or group of embodiments. Thus, whilethe present system has been described in particular detail withreference to exemplary embodiments, it should also be appreciated thatnumerous modifications and alternative embodiments may be devised bythose having ordinary skill in the art without departing from thebroader and intended spirit and scope of the present system as set forthin the claims that follow. Accordingly, the specification and drawingsare to be regarded in an illustrative manner and are not intended tolimit the scope of the appended claims.

1. A method for displaying ultrasound imaging data, the methodcomprising: generating an image from ultrasound data representative of abodily structure and fluid flowing within the bodily structure;generating vector field data corresponding to the fluid flow, whereinthe vector field data comprises axial and lateral velocity components ofthe fluid; displaying, on a user interface, a graphical representationof the vector field data overlaid on the image; extractingspatiotemporal information from the vector field data at one or moreuser-selected points within the image; and concurrently displaying thespatiotemporal information at the one or more user-selected points withthe image including the graphical representation of the vector fielddata, wherein the spatiotemporal information includes at least one of amagnitude and an angle of the fluid flow.
 2. The method of claim 1,wherein the displaying the spatiotemporal information includesdisplaying a graph of the at least one of the magnitude and the angle ofthe fluid flow at the one or more user-selected points as a function oftime.
 3. The method of claim 1, wherein the displaying thespatiotemporal information includes displaying a visual representationof a direction of the fluid flow at the one or more user-selectedpoints, and wherein the visual representation is configured todynamically update to reflect temporal changes in the direction of thefluid flow.
 4. The method of claim 3, wherein the visual representationof the direction of the fluid flow comprises a graph of the axialcomponent of the velocity vector versus the lateral component of thevelocity vector at the one or more user-selected points.
 5. The methodof claim 1, wherein the displaying the spatiotemporal informationincludes displaying information for the magnitude and the angle of thefluid flow, and wherein the displayed information and for the magnitudeand the angle of the fluid flow are synchronously updated in real-timeresponsive to the signals received from a region of interest (ROI) in asubject.
 6. The method of claim 1, wherein the graphical representationof the vector field data is a pathlet-based graphical representation ofthe vector field.
 7. The method of claim 1, wherein the graphicalrepresentation of the vector field data includes a vector map comprisinga flow mask layer delineating a sub-region corresponding to the vectorfield data, and further comprising a vector visualization layerillustrating at least partial trajectories of velocity vectors in thesub-region.
 8. The method of claim 1, further comprising estimatingelevational velocity components of the fluid to obtain three dimensional(3D) vector field data for a volumetric region of interest (ROI).
 9. Themethod of claim 8, wherein the concurrently displaying thespatiotemporal information at the one or more user-selected points withthe image includes displaying 3D image of the volumetric ROI overlaidwith the 3D vector field data.
 10. A system for visualization andquantification of ultrasound imaging data, the system comprising: adisplay unit; a processor communicatively coupled to the display unitand to an ultrasound imaging apparatus for generating an image fromultrasound data representative of a bodily structure and fluid flowingwithin the bodily structure, wherein the processor is configured to:generate vector field data corresponding to the fluid flow, wherein thevector field data comprises axial and lateral velocity components of thefluid; extract spatiotemporal information from the vector field data atone or more user-selected points within the image; and cause the displayunit to concurrently display the spatiotemporal information at the oneor more user-selected points with the image including a graphicalrepresentation of the vector field data overlaid on the image, whereinthe spatiotemporal information includes at least one of a magnitude andan angle of the fluid flow.
 11. The system of claim 10, wherein theultrasound imaging apparatus is provided by an ultrasound diagnosticsystem including the display and the processor, and wherein theultrasound diagnostic system is configured to generate and update theimage in real-time while ultrasonically imaging the bodily structure.12. The system of claim 10, wherein the processor is configured togenerate a pathlet-based graphical representation of the vector fielddata.
 13. The system of claim 10, wherein the graphical representationof the vector field data comprises a vector map including a flow masklayer defining a sub-region corresponding to the vector field data and avector visualization layer illustrating at least partial trajectories ofvelocity vectors in the sub-region.
 14. The system of claim 13, whereinthe processor is configured to define the flow mask based on imagesegmentation, available vector field data, user input, or a combinationthereof.
 15. The system of claim 14, wherein the processor is configuredto dynamically update the flow mask in subsequent image frames based ontemporal variations of the available vector field data in correspondingvector flow frames.
 16. The system of claim 10, wherein the processor isconfigured to cause the display unit to display, as the spatiotemporalinformation, a graph of the at least one of the magnitude and the angleof the fluid flow at the one or more user-selected points as a functionof time.
 17. The system of claim 10, wherein the processor is configuredto cause the display unit to display, as the spatiotemporal information,a visual representation of a direction of the fluid flow at the one ormore user-selected points, and wherein the visual representation isconfigured to dynamically update to reflect temporal changes in thedirection of the fluid flow.
 18. The system of claim 17, wherein thevisual representation of the direction of the fluid flow comprises agraph of the axial component of the velocity vector versus the lateralcomponent of the velocity vector at the one or more user-selectedpoints.
 19. The system of claim 10, wherein the vector flow data furthercomprises elevational velocity components of the fluid, and wherein theprocessor is configured to generate a three dimensional (3D) image ofthe ultrasound data overlaid with a graphical representation of a 3Dvelocity vector field.